When I play Civilization IV there are wonders that I want. Well of course I want all of them, but some are of particular interest to me. Notre Dame is one of my favorites, since early on I tend to be limited by happiness. The Hanging Gardens are oddly-placed, being of benefit in the late game when health is critical, but not as useful early on, particularly since the happiness limit means that the extra population is something between wasted and another lost soul for the whip of slavery. But I've rambled on. The point remains that as much as I like most of the wonders, never do I feel as if I am ruined by not having one, or hampered because my enemy does.

Contrast these with the wonders in Civilization V.

50% longer golden ages weren't such a bit deal in Civ IV, where golden ages were harder to generate, but are now able to be triggered at-will from the variety of great people, given as bonuses from social policies, and even built gradually from excess happiness.

The Great Wall, which was once a way to save a bit on early military costs and make defensive wars a little easier, is now a game-changer. Attackers slow to a crawl, making ranged defenders even more powerful, able to dance around and still fire away. Facing this wonder without longbowmen or artillery is a huge pain in the ass. Even with them, you're still slowed, but at least can have some influence over the battlefield.

Sistine Chapel is still essential for a cultural victory, or just to keep up, since social policies are a tech tree of their own.

There are two wonders that give a free social policy.

The Porcelain Tower is notable as well, giving a great scientist (even more powerful now that they are a free tech rather than just a large amount of science) and a large boost to research agreements. It is only the habit of the AI to declare war halfway into research agreements that keeps this wonder in check.

It might not be overpowered, but it does feel silly, the Hagia Sophia: rush it with an engineer and get it right back, and the next one a lot sooner. It's either a free wonder itself or it's another wonder free.

Machu Picchu isn't overpowered, but it is rather annoying that it is based on the luck of having a city able to build it, in a location that could build it before the game ends.